@anildash theres a thread with the founder of ghost here where they talk about being totally on board with implementing #activitypub into ghost if there were someone down to work on it. not really an answer to your question but tangentially so.
@jalcine@anildash not at all. Imagine being able to link and hashtag things within a post and have the humans on the other side be instantly notified. It enables many of the things Medium is trying to so but with out the centralized nature or capitalistic pressures.
This could be achieved with WebMentions though. For example, this is a post that's pulling in mentions (replies and likes) from Twitter and other self-hosted IndieWeb sites. All done with WebMentions - a lighter specification for all of this stuff.